4.3 Equipment Housing Vulnerabilities

To reiterate a previous point for emphasis, there will
be fluids present inside the airframe! Unfortunately, such fluids will
not immediately seek out the nearest drain and depart the aircraft.
Instead, these fluids are remarkably mobile, running along fluid conduits such
as wire bundles, hydraulic lines, control rods and waveguides. Besides
the obvious gravitational forces causing fluid movement, forces associated
with flight maneuvers, catapults, and arrestments can readily move fluids
along the various conduits. Fluids can even wick upward under certain
conditions. Table 4-3 lists those areas of the typical equipment housing which are sources of moisture and fluid intrusion. The combinations of multiple entry points, the significant mobility of fluids within an airframe, and the condensation that can occur wherever proper ambient conditions (temperature and relative humidity) prevail permits moisture and possibly other fluids to find their way to the various assemblies and boxes. The fluid can then enter equipment housings as described below.

Improved back
shell seals. Use of drip loops to relieve pressure caused by wire bundle
side loads at the back shell. Use of Water-Displacing Corrosion
Preventive Compound, MIL-C-81309, Type III on contacts. Use of
cork-and-bottle type interfacial seals. Position connectors on a
horizontal axis.